Windows on Washington wrote:Having used the Okna windows for several years now, I will tell you that we have the lowest observed rate of seal failure from that window than any other window we have used previously.

Thank you. I noticed on the Sunrise windows they fill the frame with expandable foam where Okna inserts a solid foam filler into the frame. Are there any advantages/disadvantages to either process?

+1 to both replies above. The Heat Seal spacer that Okna uses has the lowest seal failure rate of any product that I've ever observed in my personal experience, (but the XL is very good as well, particularly in the Sunrise), and there are pros and cons to both foam filling methods. The expandable foam should be superior in theory, however it has been shown that there can be air pockets/bubbles, etc causes thermal "shorts" in the process. The foam inserts have an advantage as well, just make sure that the product (like Okna) uses CNC cut foam inserts that have an EXACT fit... Ultimately, my recommendation on foam filling is to base your decision on how it affects thermal performance. Some products have no change in u-value at all, so why waste your $$$. Others, such as the Okna, drop .02-.03 points from hollow to foam filled which is a fairly significant difference... The numbers really tell the story.

Okna's spacer has a polycarbonate core which gives it tremendous rigidity and structural integrity while enabling it to expand with the glass without compromising the seal. Another benefit to the Okna spacer ,in my view, is that the spacer has a " butyl outer layer" which serves as the sealant. This eliminates the need for relying on an actual person to apply a sealant ; the glass is simply heated and pressed into the spacer using robotic equipment totally eliminating the possibility of human error.
There is nothing really wrong with injecting foam. The problem arises when the foam doesnt completely fill the extrusion which can and does happen from time to time. Its not done intentionally, its just diifucult to tell if the foam completely filled the inner core of the window. Inserting a moulded foam by hand completely eliminates that possibility.
Remember, strategically inserting foam insulated the window thus rendering better energy efficiency. Another benefit of foam is that it does add more rigidity to the frame.

I second the vote for Windows on Washington, top-notch outfit, great people. I know that they carry at least one of those lines in addition to some other top choices, I'd definitely get in touch with them.